An “ETWS (Earthquake and Tsunami Warning System)” configured to distribute emergency information such as earthquake information or tsunami information has been studied in 3GPP as a subset of a “PWS (Public Warning System).”
As shown in FIG. 7, the ETWS includes a network node (including, for example, a radio base station eNB or the like) 1, an emergency information distribution server 3 and a mobile station UE.
In the ETWS as shown in FIG. 8, the emergency information distribution server 3 transmits a “Disaster Notification (emergency information)” indicating that a disaster has occurred, to the network node 1 in step S1001.
In step S1002, the network node 1 notifies multiple mobile stations UE that the disaster has occurred, by using a “First Notification (paging signal).”
When receiving the “First Notification,” the mobile stations UE each perform output (such as buzzer output, alarm output or displaying on a display) for the “First Notification.”
In step S1003, the network node 1 notifies the multiple mobile stations UE of detailed information on the disaster by using a “Second Notification.”
Note that each mobile station UE receives the “Second Notification” based on information designated by the aforementioned “First Notification,” and displays the detailed information on the display, the detailed information being notified by using the “Second Notification.”
Since the aforementioned ETWS has a possible threat such as transmission of a “Fake First Notification (paging signal)” by an invalid radio base station, the aforementioned First Notification needs to be transmitted to the mobile station UE by secure communication.
In the configuration of ETWS shown in FIG. 7, it is assumable that the “Disaster Notification” is transmitted by secure communication using a dedicated line or IPsec, through an interface between the network node 1 and the emergency information distribution server 3, whereas there is a problem that the “First Notification (paging signal)” cannot be transmitted by security communication, through a radio interface between the network node 1 and the mobile station UE.
Specifically, a radio link for security communication is not established between the network node 1 and the mobile station UE at the time of transmitting the “First Notification (paging signal).” For this reason, the “First Notification (paging signal)” cannot be transmitted by security communication, through the radio interface between the radio base station eNB and the mobile station UE.
In addition, even if the link for security communication is established between the mobile station UE and the network node 1 such as the radio base station eNB, an exchange MME or gateway device S-GW, security cannot be provided using security information individually established for each mobile station UE by the network because the multiple mobile stations UE receiving the same paging signal each need to determine whether or not the received paging signal is directed thereto.